1. Field of the Invention
The present invention relates generally to pollution control equipment and, more particularly, is concerned with an apparatus and method for spray drying solids-laden high temperature gases.
2. Description of the Prior Art
Hazardous waste incinerators and other high temperature furnaces exhaust hot gases laden with flyash. The energy in these hot gases is available to be used in a spray drying apparatus for spray drying liquids containing dissolved solids to produce cooled exhaust gases and dry powder which contains the previously dissolved solids.
Using exhaust gases from these different sources after substantial reduction in the gas temperature is common practice in a spray drying apparatus. It is not conventional practice, however, to have exhaust gases enter the vessel of the spray drying apparatus at very high temperatures under conditions where the exhaust gases may contain molten flyash and where conventional flow distribution devices cannot be used.
Flow distribution within the vessel of the spray drying apparatus is an important factor in spray drying vessel design. Various types of distribution plates, straightening vanes, and similar devices are used to make the velocity profile across the spray drying vessel as uniform as possible. If the gas flow is not uniformly distributed, then partially dried solids will impact the wall of the vessel and build up deposits which will lead eventually to shutdown.
At high temperatures when flyash is present, these flow distribution devices are impractical and inappropriate to use. Metals lose structural strength and are rapidly oxidized. Ceramics are hard to support and fabricate. Both metals and ceramics contain openings which are rapidly clogged with flyash.
Consequently, a need exists to devise other ways to more uniformly distribute the high temperature gas flow in the spray drying vessel.